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From Ash Berlin-Taylor <>
Subject Re: Making Airflow Timezone aware
Date Mon, 13 Nov 2017 18:47:32 GMT
This sounds like an awesome change!

I'm happy to review (will take a look tomorrow) but won't be a suitable tester as all our
DAGs operate in UTC.


> On 13 Nov 2017, at 18:09, Bolke de Bruin <> wrote:
> Hi All,
> I just want to make you aware that I am creating patches that make Airflow timezone aware.
The gist of the idea is that Airflow internally will use and store UTC everywhere. This allows
you to have start_date = datetime(2017, 1, 1, tzinfo=“Europe/Amsterdam”) and Airflow will
properly take care of day light savings time. If you are using cron we will make sure to always
run at the exact time (end of interval of course) which you specify even when DST is in effect,
e.g. 8.00am is always 8.00am regardless of if a day lights savings time has happened. DAGs
that don’t have a timezone associated, get a default timezone that is configurable.
> In AIRFLOW-288 I am tracking what needs to be done, but I am 80% there. As the patches
are invasive particularly in tests (everything needs a timezone basically) less so in other
areas I like to raise special attention to a couple of places where this has impact.
> 1. All database DateTime fields are converted to timezone aware Timestamp fields. This
impacts MySQL deployments particularly as MySQL was storing DateTime fields, which cannot
be made timezone aware. Also, to make sure conversion happens properly we set the connection
time zone to UTC. This is supported by Postgres and MySQL. However, it is not supported by
SQLServer. So if you are running outside of UTC you need to take special care when upgrading.
> 2. Thou shall not use and datetime.utcnow() when writing code for core
(operators, sensors, scheduler etc) Airflow (in DAGs your can still use it). Both create naive
date times (yes even utcnow() ). You can use airflow.utils.timezone utcnow() for this. As
you will not be able to store naive datetime fields anymore you will notice soon enough.
> Finally, and that is the main reason fir this email, I am looking for feedback and testers.
The PR can be found here: it doesn’t
pass the tests yet, but you can see that I am working hard on that ;-).
> Cheers
> Bolke

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